The present invention relates to a power supply arrangement for a portable information processing apparatus such as a laptop computer.
Due to recent advanced semiconductor integration technology and packaging technology, hand-held and portable information processing apparatuses such as laptop computers or the like are becoming more prevalent. Such apparatuses, as described in Japanese Laid-Open Patent Application No. 61-218326, are basically battery operated, and are designed to connect with an a.c. adapter so that they operate by an a.c. power source or for connection with an external battery charging unit, as shown in FIG. 2 which is representative of the prior art.
FIG. 2 illustrates a main unit 1 of the information processing apparatus (hereinafter termed the "main unit"), an a.c. adapter 2, an a.c. cable 4, and a d.c. power cord 5 which supply power to the main unit. An expansion unit 3, such as a floppy disk unit is connected externally to the main unit 1, and a signal cable 6 connects the expansion unit 3 to the main unit. Conventionally, when the main unit 1 is used as a stand-alone equipment, it operates by the internal battery, or when it is used in connection with the expansion unit 3, it is further connected with the a.c. adapter 2 so that power is supplied from the a.c. adapter 2 instead of the battery in the main unit 1. The reason for this operational condition is that equipping the main unit 1 with a battery having sufficient power to drive the expansion unit 3 increases the weight and also the cost of a main unit 1. Since the weight and price of a portable apparatus are crucial factors for the user in choosing a model, conventionally, the battery built in the main unit 1 has its capacity limited to the minimum requirement.
The foregoing conventional technique, when the expansion unit is connected to the main unit, necessitates supply of power from the main unit to the expansion unit through the connection of an a.c. adapter. As a result, the number of cables running out of the main unit increases, which not only spoils the look of the operational environment, but also compels the user to labor in connecting and disconnecting the a.c. adapter to the main unit each time the apparatus is transported for use.